Commit dc313385 authored by Vitaly Kuznetsov's avatar Vitaly Kuznetsov Committed by Paolo Bonzini
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KVM: nVMX: Reset eVMCS clean fields data from prepare_vmcs02() 



When nested state migration happens during L1's execution, it
is incorrect to modify eVMCS as it is L1 who 'owns' it at the moment.
At least genuine Hyper-V seems to not be very happy when 'clean fields'
data changes underneath it.

'Clean fields' data is used in KVM twice: by copy_enlightened_to_vmcs12()
and prepare_vmcs02_rare() so we can reset it from prepare_vmcs02() instead.

While at it, update a comment stating why exactly we need to reset
'hv_clean_fields' data from L0.

Signed-off-by: default avatarVitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Message-Id: <20210526132026.270394-10-vkuznets@redhat.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent b7685cfd

arch/x86/kvm/vmx/nested.c

+13 −6
Original line number Diff line number Diff line
@@ -2059,14 +2059,10 @@ void nested_sync_vmcs12_to_shadow(struct kvm_vcpu *vcpu) 
{

	struct vcpu_vmx *vmx = to_vmx(vcpu);



	if (evmptr_is_valid(vmx->nested.hv_evmcs_vmptr)) {

	if (evmptr_is_valid(vmx->nested.hv_evmcs_vmptr))

		copy_vmcs12_to_enlightened(vmx);

		/* All fields are clean */

		vmx->nested.hv_evmcs->hv_clean_fields |=

			HV_VMX_ENLIGHTENED_CLEAN_FIELD_ALL;

	} else {

	else

		copy_vmcs12_to_shadow(vmx);

	}



	vmx->nested.need_vmcs12_to_shadow_sync = false;

}
@@ -2616,6 +2612,17 @@ static int prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12, 


	kvm_rsp_write(vcpu, vmcs12->guest_rsp);

	kvm_rip_write(vcpu, vmcs12->guest_rip);



	/*

	 * It was observed that genuine Hyper-V running in L1 doesn't reset

	 * 'hv_clean_fields' by itself, it only sets the corresponding dirty

	 * bits when it changes a field in eVMCS. Mark all fields as clean

	 * here.

	 */

	if (evmptr_is_valid(vmx->nested.hv_evmcs_vmptr))

		vmx->nested.hv_evmcs->hv_clean_fields |=

			HV_VMX_ENLIGHTENED_CLEAN_FIELD_ALL;



	return 0;

}